Warternberg syndrome is mainly ulnar nerve involvement, PT cannot add little finger according to Magee. I also saw that it can be a radial nerve compression. Which one is true?

The confusion possibly arises because there is both a Warternberg SYNDROME as well as a Warternberg SIGN.

Wartenberg’s Syndrome is described as the entrapment of the superficial branch of the radial nerve with only sensory manifestations and no motor deficits. On the other hand, Wartenberg’s Sign refers to the slightly greater abduction of the fifth digit, due to paralysis of the abducting palmar interosseous muscle and unopposed action of the radial innervated extensor muscles (digiti minimi, digitorum communis) secondary to Ulnar nerve palsy.

Reference 1, Reference 2